Variable displacement pump



May 18, 1965 R. E. RAYMOND 3,

VARIABLE DISPLACEMENT PUMP Filed Dec. 22-, 1961 7 Sheets-Sheet 1 INVENTOR. 10055427 2 RAY/"0ND BY CW4?- 1% 41/: 4770 NE):

May 18, 1965 R. E. RAYMOND VARIABLE DISPLACEMENT PUMP 7 Sheets-Sheet- 2 Filed Dec. 22, 1961 f ,154 I64 I92 Filed Dec. 22, 1961 E. RAYMOND VARIABLE DISPLACEMENT PUMP 7 Sheets-Sheet 3 Q N L *2: 5 N r V I l 3 l I Q I 8| I E I l N a 3 6 L Q. 4 Q INVENTOR. N Q aoamrr. RAYMOND M3 ATTNEYS May 18, 1965 R. E. RAYMOND VARIABLE DISPLACEMENT PUMP 7 Sheets-Sheet 4 Filed Dec. 22, 1961 INVENTOR. ROBE/Q7 [.KAYMOND l/IS ATTORNEYS 1955 R. E. RAYMOND 3,183,847

VARIABLE DISPLACEMENT PUMP Filed Dec. 22, 1961 7 Sheets-Sheet 5 INVEN TOR. ROBERT E. RAYMOND 52M ya #2.

ATTORNEYS May 18, 1965 R. E. RAYMOND VARIABLE DISPLACEMENT PUMP 7 Sheets-Sheet 6 Filed Dec. 22. 1961 INVENTOR.

ROBERT E. RAYMOND 7 ATTORNEYS y 1965 R. E. RAYMOND 3,183,847

VARIABLE DISPLACEMENT PUMP Filed Dec. 22. 1961 7 Sheets-Sheet 7 I92 5 l35-A C) I5OA 0 2o2 Q as I G 3|2 I /e2 A INVENTOR. ROBERT E. RAYMOND ATTORNEYS United States Patent C) 3,183,847 VARIABLE DISPLACEMENT PUMP Robert E. Raymond, Zanesville, Ohio, assignor to Hydro- Kinetics, Inc., Zanesville, Ohio, a corporation of Ohio Filed Dec. 22, 1961, Ser. No. 161,554 14 Claims. (Cl. 1l)3173) This application is a continuation-in-part of my copending application Serial No. 111,99, filed May 23, 1961, now abandoned.

This invention relates generally to hydraulic machines and particularly to a novel piston type variable displacement pump.

In general, the pump of the present invention comprises a housing means that includes an axially shiftable cylinder barrel and a plurality of pistons mounted for axially reciprocating movement in the cylinder barrel. The variable flow delivery from the pump is accomplished by axially shifting the cylinder barrel and intake ports relative to the pistons.

As one aspect of the present invention, a single axially shiftable cylinder barrel, in combination with a plurality of axially disposed pistons, performs eight major pumping functions as follows:

(1) Provides cylinder chambers for pistons.

(2) Absorbs piston side reaction force;

(3) Provides axially shiftable inlet valve ports.

(4) Supportsoutlet valve assemblies.

(5) Supports the piston return means.

(6) Provides variable fiow delivery by being axially shiftable relative to the pump housing.

(7) Includes flat surface in sliding sealed engagement with pressure biased outlet members for delivering oil 1 from the axially shiftable cylinder barrel to the stationary pump housing.

(8) Provides a manifold for collecting oil from a plurality of the cylinders.

As another aspect of the present invention, the pump including novel apparatus for transferring oil from the axially shiftable cylinder barrel to the stationary pump housing which apparatus includes novel pressure biased hollow outlet members movably mounted in the pump housing and in sliding sealed engagement with the cylinder barrel.

As another aspect of the present invention, the pump includes novel mounting means for supporting the axially shiftable cylinder barrel in the pump housing, said mounting means being in the form of longitudinally extending rail bearings that not only absorb piston side thrust but, in addition, absorb torque and serve as keys against barrel rotation.

As another aspect of the present invention, the pump includes novel apparatus for axially shifting the cylinder barrel relative to the pump housing in the form of an annular piston that moves the cylinder barrel in opposition to an opposing force exerted by a control spring.

As another aspect of the present invention, the pump includes novel means for transferring piston thrust reaction forces to the pump housing in the form of a plurality of reaction plugs which serve to isolate the cylinder barrel from pulsating piston forces.

As another aspect of the present invention, the pump includes a plurality of reaction plugs which are self-aligning since they freely engage the pump housing at any location dictated by the position of the cylinder barrel on its longitudinally extending rail bearings. This eliminates costly alignment problems.

As another aspect of the present invention, the pump includes a plurality of reaction plugs that not only serve to transfer individual piston reaction forces to the pump housing but also serve the additional functionof housing outlet check valve assemblies.

3,183,847 Patented May 18, 1965 As another aspect of the present invention, the pump includes a novel variable displacement control spring arrangement whereby a single control spring is utilized to bias the cylinder barrel in one axial direction to provide a variable displacement control force. The same control spring also serves to bias the previously mentioned reaction plugs against the pump housing.

As another aspect of the present invention, the pump comprises a novel piston return apparatus that forces the piston to follow a driving cam. This apparatus includes a yoke that engages each piston, a yoke reaction plug mounted in the cylinder barrel, and a yoke reaction spring for biasing the plug and yoke against the pistons. This eliminates the need for individual piston return springs and permits a more compact apparatus.

As another aspect of the present invention, the pump comprises a novel composite piston shoe construction formed of nylon or the like surrounded by a steel casing, the latter being crimped around a ball shaped base on the piston. This shoe construction serves the dual function of preventing the nylon shoe portion from splitting and retaining the shoe on the piston. This results in a piston shoe with sufiicient compression strength and a low coefficient of friction. Moreover, the shoe is self-aligning and accommodates foreign materials Without abrading the driving cam.

As another aspect of the present invention, the pump includes a novel control apparatus that automatically meters a control flow of oil to the previously mentioned annular piston that shifts the cylinder barrel. The control apparatus is adapted to automatically vary the effective stroke of the pistons responsive to variations in the outlet pressure to the load whereby oil is delivered to the load at substantially constant pressure.

As another aspect of the present invention, the control apparatus mentioned in the previous paragraph can readily be removed and other control apparatus substituted therefor, to establish other desired conditions at the load other than the substantially constant pressure conditions provided by the control apparatus discussed in the previous paragraph.

As another aspect of the present invention, the pump is modified to include a novel shock relief apparatus for the variable displacement control mechanism which a-pparatus is responsive to excessive rates of change of pressure and to excessive flow rates. Thisshock control apparatus comprises a modified pressure biased hollow outlet member that includes a shock detection plate provided with an orifice of sufiicient size to accommodate higher rates of flows encountered during shock conditions.

As another aspect of the present invention, the pump can be provided with modified pumping pistons that in clude check valves and a modified cylinder barrel that includes a main intake port and a by-pass port. These modifications eliminate cavitational operation and yet permit normal variable displacement operation.

As another aspect of the present invention the pump, in one of its modifications, includes a plurality of reaction action pins slideably mounted in the axially shiftable cylinder. barrel. posed to pressurised fluid in the exhaust manifold and outer ends engaging the pump housing whereby the hydraulic force exerted on the housing through the reaction pins biases the cylinder barrel against an annular control piston that provides the force for varying the position of the cylinder barrel in the housing.

As another aspect of the preesnt invention, one modification of the pump includes an annular cylinder barrel driving cylinder that extends circumferentially around the casing of the pump and includes an intake opening for a relatively hot flow of control oil and an outlet passage, on the opposite side of the casing means, for releasing These reaction pins include inner ends exa the control flow to the exterior of the casing means. This annular cylinder and passage arrangement not only serves to cool the relatively hot control flow of oil by passing it circumferentially around the outer regions of the casing, in heat exchange relationship with the environment, but also provides built in means for delivering the control flow from a control mechanism mounted on the top of the casing means to a subplate mount on the bottom of the casing means from where the control flow can be conveniently returned to an external reservoir.

As still another aspect of the present invention, the pump includes an axially shiftable cylinder barrel provided with an integrally moulded manifold that functions in a novel manner to collect the outlet oil from the cylinders and transfer it to the pump housing in a unique manner.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred forms of embodiments of the invention are clearly shown.

In the drawings:

FIG. 1 is a side sectional view of a variable displace ment pump constructed in accordance with the present invention, the section being taken along the plane 11 of FIG. 3;

FIG. 2 is an end sectional view of the pump of FIG. 1, the section being taken along the line 2-2 of FIG. 1;

FIG. 3 is a top elevational view, partially in section, of the pump of the preceding figures; the section being taken along the line 33. of FIG. 1;

FIG. 4 is a partial sectional view of the pump of the preceding figures with a surge control apparatus mounted thereon, the section being taken along the vertical plane through the center of the pump;

FIG. 5 is a side sectional view of a modified cylinder barrel and piston assembly for the pump of the preceding figures, the section being taken along a vertical plane through the center line of the assembly;

FIG. 6 is an end elevational view of a modified piston comprising a portion of the assembly of FIG. 5;

FIG. 7 is a side elevational view of the modified variable displacement pump constructed in accordance with the present invention, this section being taken along the line '77 of FIG. 9;

FIG. 8 is an end sectional view of a cylinder barrel comprising a portion of the apparatus of the modified pump of FIG. 7, the section being taken along the line 88 of FIG. 7; and

FIG. 9 is an end sectional view of the pump of FIG. 7,,

the section being taken along the line 99 of FIG. 7;

Referring in detail to the drawings a variable displacement pump constructed in accordance with the present invention is illustrated in FIGS. 1-3 and comprises a housing means indicated generally at 28 that includes a front housing portion indicated generally at 22 and a rear housing portion indicated generally at 24. The two casing portions are joined together at the central portion of the pump by a plurality of studs 26 seen in FIGS. 2 and 3.

A drive shaft is mounted in the forward end of the housing means by tapered roller bearing assemblies 30 and 32 which assemblies are pressed into recesses 34 and 36. v

An oil seal 38 is pressed into a recess 40 in the housing and includes an annular resilient element 42 that Wipes the periphery of drive shaft 28.

As seen in FIG. 1 the inner end of drive shaft 28 carries a cam means generally at 44 which includes a central bore 46 provided with a keyway 48 that receives a key 50 for preventing rotation of a cam means relative to shaft 28. The cam means is retained on shaft 28 by a pair of nuts 52 which are tightened into lock relationship on a threaded inner end portion on shaft 28.

With continued reference to FIG. 1, cam means includes an inclined surface 54 which engages a plurality of nylon shoes 55, the latter including sockets 58 which form pivotal ball joints with ball-shaped ends 60 formed on a plurality of pumping pistons 62.

Each of the nylon piston shoes 56 is surrounded by a metal casing 64 that is crimped around the ball-shaped end 60 of its respective piston. Each metal casing 64 also includes an inwardly extended annular protrusion es that snaps into an annular recess 68 formed in the base of the nylon shoe portion. 7

With reference to FIGS. 1 and 2, a cylinder barrel indicated generally at 70 is axially slideably mounted within the casing means by means of a plurality of guide Qronvee. 72 and 74 which receive longitudinally extending bearing members '76.

The members 76 may best been described as side rail bearings and their function to not only absorb piston side thrust reaction imposed on the cylinder barrel but, in addition, these side rail bearings function as keys against cylinder barrel reaction and thereby serve to absorb torque.

Side rail bearings 76 are of substantially the same length as cylinder barrel 70 and are preferably formed of nylon or other similar synthetic rod material.

Pistons 62 are disposed in respective barrel cylinders 78 which receive low pressure oil or hydraulic fluid via intake 80in base 82, passage 84 in front housing portion 22, the inner chamber 86 within the housing and the intake ports for each cylinder, two of which are seen at 88 and 88-A in FIG. 1.

Intake port 88-A is shown with its respective piston 62 at the bottom of a stroke at which position the piston has uncovered intake port 88-A and drawn fluid into its cylinder. Intake port 88, however, is closed since its respective piston is at the top of its stroke.

As seen in FIGS. 1 and 2, each of the cylinders '78 includes a respective reaction plug, indicated generally at 90, in free self-aligning engagement with the inner end surface 92 of rear housing portion 24.

Each reaction'plug is provided with a central bore 94 that carries an outlet ball check valve 96 which is freely retained in bore 94 by a threaded plug 98.

Each threaded plug 98 includes a seat portion 108, a longitudinal passage 182, and a radial passage 103, the latter communicating with an annular passage 104 formed in the outer wall of reaction plug 90.

With continued reference to FIG. 1, the bore 94 in each reaction plug 90 includes a valve stop 106 and a compression spring 108 which serves to limit the stroke of the ball and bias it towards a closed position.

Pressurized oil from cylinders 78 is discharged to the exterior of the pump, in a unique manner, through a pressure biased outlet member 110 which includes a central passage 112 that communicates with high pressure discharge passage 114 that in turn leads to an outlet hole 116 formed in base 82.

As seen in FIG. 1, outlet member 110 includes a foot portion provided with a surface 118 that is in slideable sealed engagement with a longitudinally extending surface 128 formed in the outer wall of cylinder barrel 70.

It will be noted from FIG. 1 that when cylinder barrel 70 is axially shifted relative to the housing means 20 an outlet port 122 formed in the cylinder barrel always remains in communication with central passage 112 in outlet member 110 notwithstanding axial movement of cylinder barrel 70.

With continued reference to FIGS. 1 and 2, pressure biased outlet member 110 includes a piston surface 124 that causes the pressurized hydraulic fluid in passage 112 to bias the surface 118 on outlet member 110 downwardly into sealed engagement with longitudinally extending surface on barrel 70. If desired, outlet member 118 can be structurally modified so as to be hydraulically balanced in accordance with the teachings in my copending application.

A spring 126 augments the biasing force of the high pressure oil on piston surface 124 and also serves to retain surface 118 in sealed engagement with surface 120 at low pressures and at the outset of operation.

The outer peripheral surface of outlet member 110 is provided with an annular seal 128 and a threaded plug 129 is screwed into the hole forming passage 112 and includes an inner protrusion that forms a retainer for the end of spring 126.

With reference to FIGS. 1 and 2, pressurized oil from the pumping cylinders 78 is released from longitudinal passages 102 in reaction plugs 90 via a plurality of small radially extending passages 103, FIG. 2, annular recesses 104, an annular manifold 134, cylinder barrel outlet port 122, radial passage 112 through outlet member 110, passage 114, and base outlet hole 116 to the load.

Pressurized oil is also released to a variable displacement hydraulic control unit indicated generally at 135 by a second pressure biased outlet member 119-A, FIGS. 1 and 2, which is identical to outlet member 110 previously described. I will be noted that outlet member 110-A includes a base surface 136 that is hydraulically biased into sealed engagement with a longitudinally extending surface 138 formed in the outer wall of cylinder barrel 70. Outlet member 11ii-A is biased downwardly against longitudinally extending surface 138 by a force exerted by a piston surface 124, pressurized oil in a passage 140.

Referring to FIG. 1, cylinder barrel 70 is constantly biased towards the front of the housing means by a control spring 142 which is interposed between a spider 143 and an annular shoulder 145 formed on cylinder barrel 70.

Cylinder barrel 70 is hydraulically shifted axially against the biasing force of control spring 142 by means of an annular cylinder barrel driving piston indicated generally at 146 in FIG. 1. Piston 146 is mounted in a cylindrical surface 148 and forms therewith control cylinder 150 for receiving pressurized oil in a manner later to be described. A small annular piston surface 152 of larger diameter provides sufiicient axial force with low control pressures to shift cylinder barrel 70 against the force of control spring 142.

With continued reference to FIG. 1, piston 146 includes a rear end 155 in forced transmitting engagement with an annular base portion 157 on cylinder barrel 7%.

Referring particularly to FIGS. 1 and 3, pressurized oil is delivered through the control apparatus 135 to the barrel driving piston and cylinder 146-150 via passage 140, passage 144, orifice 147, ,spool cylinder 149, radial passage 130 in spool housing 151, lateral passage 154 in control block 156, longitudinal passage 158 in control block 156, vertical passage 160 in control block 156, and passage 162 in the pump housing which connect to control cylinder 151).

The above described. passages for conducting the control flow of oil to control cylinder 150 are diagrammatically illustrated in FIG. 4.

Referringparticularly to FIGS. 1 and 2 spool housing 151 carries a longitudinally shiftable spool member 164 that is normally biased towards a closed position by a spring 166, the latter being contained in a spring housing 168 that is threaded into control block 156 at a threaded hole 170. Compression spring 166 is selectively compressed by manipulating a control knob 172 that includes a shank 174 in threaded engagement with spring housing 168 at a threaded hole 176. As seen in FIG. 1, a radial passage 178 extends through control block 156 and rear housing portion 24 to provide a drain back to the tank for any hydraulic fluid that may leak between the outer surface of control spool 164 and the inner surface of'spool cylinder 149.

With reference to FIG. 3, the down stream control pressure for the control circuit is limited to some predetermined low pressure valve by a ball check valve 180 6 which communicates with the control circuit via a pas sage 182 in control block 156 and is biased towards its seat 184 by a compression spring 186. A threaded plug 188 in hole 190 provides means for installing relief valve 180 and also serves as a spring retainer.

With continued reference to FIG. 3, and the diagrammatic portion of FIG. 4, a small flow of oil is continuously drained back to tank via a small orifice 232 and radial passage 226. Momentary high flows during shock conditions are drained back to tank via check valve 180 and passage 226.

Control block 156 is mounted on housing 21) by means of a plurality of studs 192 as seen in FIG. 3. It will be understood that other types of control apparatus suitable for various types of load conditions, can be readily mounted on the pump merely by unscrewing the studs and replacing control block 156 with a modified version.

The pumping pistons 62 are returned and biased against eccentric 44 in a novel manner, by means of a single centrally disposed piston return rod 194, FIG. 1, which includes an arcuate socket 196. A ball 193 fits into socket 196 of rod 194 and also into a socket 260 formed in a piston return yoke 202. Yoke 2112 includes a plurality of radially extending slots 2114 that fit around neck portions 206 and the bases of the pistons 62. Piston return yoke 202 applies force to the rear sides of the ball-shaped piston ends 6% and in turn receives force from piston return rod 194 via the pivot joint formed by ball 19% and sockets 196 and 200. A compression spring 210 is disposed between a shoulder 214 on the rear end of piston return rod 194 and a shoulder 215 on a spring retainer plug 216 which in turn bears against the front side of spider 143. Spider 143 is restrained from rearward movement by the shoulders 221) formed on the ends of reaction plugs 96. It should be pointed out that reaction plugs 99 are fitted loosely int-o respective holes 222 in spider 143 and are in free engagement with the inner surface 92 of the housing whereby the plugs are self-aligning with respect to pump cylinders 73.

The ends of passages 154 and 158 in control block 156 are closed by threaded plugs 224 and 225 respectively.

Reference is next made to the FIG. 4 which illustrates a modified control apparatus indicated generally at 259 which includes shock relieving apparatus. The shock relief feature is provided by adding a shock detection plate 252 provided with a relatively small orifice 254 to a modified pressure biased outlet member -B. During normal operating conditions orifice 254 is large enough to handle the control flow and outlet member 110-8 remains pressure biased downwardly into sealed engagement with surface 138 due to the outlet pressure exerted on piston surface 124.

During shock conditions, however, the high rates of flow exceed the capacity of orifice 254 and develop large forces across shock detector plate 252 in a direction that lifts outlet member 110-B away from surface 138 on the cylinder barrel. When outlet member 110-B separates from the cylinder barrel, the high volumetric shock flow passes between member 119-13 and surface 138 and into the low pressure zone of the housing. When the shock condition subsides spring 126 and the unbalanced hydraulic force on outlet member 110-B return it immediately into sealed engagement with surface 138 on the cylinder barrel.

The components of control apparatus 256 which correspond to those previously described in connection with control apparatus are designated by identical numerals. The passages, valves, and orifice leading to control cylinder, are illustrated diagrammatically.

iFIG. 4 includes a modified control pressure adjusting screw 172-A that includes an elongated shank portion 174-A on which is mounted a calibrating cylinder 256 provided with indicia for selectively setting control screw 172-A ata predetermined control pressure setting.

Reference is next made to FIG. which illustrates a modified piston and cylinder block arrangement which prevents cavitationand can be utilized, at additional expense, where extremely low noise levels are desired.

The apparatus of FIG. 5 includes a modified cylinder barrel 70-A provided with a main intake 262, which han dies the main intake flow, and a small by-pass port 264.

Withcontinued reference to FIG. 5, the assembly includes a modified piston 62-A provided with an annular recess 266 that at all times communicates with main inlet port 262.

Piston 62-A includes a valve cavity 268 that contains a check valve 275 normally biased against its seat by a compression spring 272. The ball is retained in the cavity by a plug 274 held in place by a snap ring 276.

As is best seen in FIG. 6, plugs 274 includes a central passage 278 and peripheral slots 230 that communicate with main intake port 262 via transverse passage 282 when check valve 2 711 is open on the suction stroke.

In operation, when the pump of FIGS. 1-3 is driven by a prime mover cam 44 reciprocates pistons 62 which, on the suction stroke, draw oil into the cylinders 78 via inlet passage 84, chamber 86 formed by housing 20, and intake ports 88.

On the compression stroke pistons 62 deliver oil from cylinders '78 to outlet port 116 via passages 102 in plugs 98, check valves radial passages 103, annular grooves 104, manifold 134, passage 112 in hollow outlet member 116, outlet passage 114, the outlet port 116 connected to the load.

Some of the pressurized oil in manifold 134 is delivered to variable displacement control apparatus 135 for shifting annular piston 146 and cylinder barrel 70 in the manner previously described.

A constant pressure at the load is obtained by arranging spool 164 to open only when a predetermined selected load pressure is exceeded. Control knob 172 is adjusted to compress spool control spring 166 so as to bias spool 164 with the proper force to permit its opening when the predetermined selected operating pressure is exceeded. When the pressure at the load rises above the operating pressure oil from the manifold passes through passage 144 and orifice 147 to spool cylinder 149. The increased pressure in the spool chamber overcomes the preset control force exerted by spool control spring 166 whereby the spool is shifted to the left, as viewed in FIG. 1, and oil is released through radial passages 130 in spool housing 151 and thence through the previously described passages to the control cylinder 150. This shifts annular piston 146 and cylinder barrel 70 to the left, as viewed in FIG. 1, whereby intake ports 88 are moved to the left, relative to piston 62. This decreases the efiective strokes of the pistons since the intake ports 88 are closed later in the return stroke of the pistons whereby a smaller charge of oil is translated. When less oil is being pumped per piston compression stroke the pressure is automatically cut back and when the pressure drops to the preselected control pressure the biasing force exerted by spool control spring 166 shifts spool 164 to the right, as viewed in FIG. 1, whereby the spool closes radial ports 130 and the flow of oil to control cylinder is terminated.

Since control cylinder 150 is always exposed to low flow rate leakage back to tank via orifice 232 and passage 226, previously described, control spring 142 can shift cylinder barrel 70 and barrel driving piston 146 towards the right, as viewed in FIG. 1, and thereby shift intake port 88 to the right to provide a longer effective stroke for each piston. When this occurs, more oil is delivered to the load per piston stroke. It will, therefore, be understood that control spring 142 constantly biases the pump apparatus towards a higher pressure producing configuration. As soon as the predetermined desired load pressure is exceeded, however, the previously described pressure reducing action of spool 164 occurs.

In view of the above, it will be understood that the pump operates with spool 164 in a threshold configuration relative to radial passages 130. The moment the manifold pressure exceeds the predetermined pressure desired at the load, spool 164 departs from its threshold position and opens to release oil to controlcylinder 159. Conversely, the moment the manifold pressure drops below the predetermined value desired at the load spool 164 maintains radial passages closed whereby oil can drain from control cylinder and permits control spring 142 to drive cylinder barrel 70 to the right, as viewed in FIG. 1. This increases the volumetric delivery of oil per piston stroke whereby the pressure at the load is returned to the predetermined value.

The operation of the modification of FIG. 4 is identical to that of the modification of FIGS. 1-3 with the exception that the FIG. 4 pump is adapted to relieve shock conditions by the inclusion of a shock relief apparatus in the form of a modified hollow outlet member 110-13 provided with a shock detection plate 252. Under normal flow conditions, a small orifice 254 handles the control fiow and the lower surface of outlet member 110-B is maintained in sealedsliding engagement with surface 138 onthe cylinder barrel. During shock conditions, however, shock detector plate 252 is 'responsiv'e to excessive fluid flow to the control apparatus or to excessive rates of change of system pressure since orifice 254 is too small to handle flow-rates at excessive rates of pressure increase. Large forces are in these instances developed across shock detection plate 252 in a direction which separates hollow outlet member 110-3 and the shock flow is then released to the crank case of the pump. When the shock conditions terminates, spring 126 and the unbalanced hydraulic forces on outlet member 1111-13 immediately return the outlet member into sealed sliding engagement with the cylinder barrel and the pump resumes normal operation.

The operation of the pump when modified in accordance with FIG. 5 is identical to that previously described except that cavitation operation is eliminated by maintaining the main suction port 262 at all times in communication with a ball check valve 270 whereby the piston can draw oil into the cylinder throughout its entire suction stroke. Some oil also flows into the cylinder through the smaller by-pass port 264 during the suction stroke.

When piston 62-A reaches bottom dead center and starts on its power stroke the pumping of oil commences as soon as the piston closes smaller by-pass port 264. Since the position of smaller by-pass port 264 is varied, depending on the position of cylinder barrel 70-A, it will be understood that variable displacement control is achievedby moving smaller by-pass port 264 in the same manner. as such control was achieved by moving intake ports 88 of the pumps of the preceding figures.

With continued reference to FIG. 5, it will be understood that the suction characteristics of the pump are not affected by movement of cylinder barrel 70-A since main intake port 262 is always in communication with the interior of the cylinder, on the suction stroke, via recess 266, passage 282, check valve 271i,v and passage 278 and slots 280.

Reference is next made to FIGS. 7-9 which illustrate a modified variable displacement pump constructed in accordance with the present invention.

The structural components of the modified portion of FIGS. 7-9 which are identical to the structural components of the pump of FIGS. 1-3 are designated by identical numerals and the description previously set forth herein, relatively to the modifications of FIGS. 1-2, also applies to the modification of FIGS. 7-9.

With reference to FIGS. 7 and 8, the pump includes a modified cylinder barrel indicated generally at 300 that comprises a modified annular exhaust manifold 134-A which communicates with the inner ends of a plurality of bores 302. Each of the bores slidably carries a reaction pin 3194 that includes an outer end in force trans- 9 mitting engagement with spider 143 which in turn abuts the rear wall of the housing means.

In operation of the embodiment of FIGS. 7-9 the pressurized oil in annular exhaust manifold 134-A exerts a force on the inner ends of reaction pins 304 which force is equal to the product of the exhaust pressure and the cross sectional area of the reaction pins. This hydraulic force augments the mechanical force exerted on cylinder barrel 300 by control spring 142 and hence can be utilized to reduce the mechanical spring force required to counteract the barrel shifting force exerted by control cylinder ISO-A.

It should be pointed out that control spring 142 is required, in addition to the hydraulic force exerted by the reaction pins, since the hydraulic force is not present at the starting of the pump.

Reference is next made to FIGS. 7 and 9 which illustrate a novel control flow cooling and exhausting structural feature added to this modified version.

The modification of FIGS. 7-9 includes a modified annular control cylinder 150-A having an outlet passage 312 which provides a dynamic control circuit through the control cylinder in the embodiment of FIGS. 1-3. This means that the relatively hot pressurized control flow entering the top of the control cylinder through control passage 162 passes circumferentially around the outer regions of the pump casing in heat exchange relationship with the environment, whereby the control flow is cooled. Moreover, the control flow is transferred from the control mechanism 135-A on the top of the pump to the modified subplate 82-A on the bottom without the useof external tubing.

At this point it should be pointed out that the control flow in the embodiment of FIGS. 1-3 is returned to the interior of the pump via flow rate control orifice 232, FIG. 3, the vertical passage 226 communicating with the low pressure portion of the casing means.

With the embodiment of FIGS. 7-9 the flow rate control orifice 232-A in flow control mechanism 135-A is either eliminated or plugged and replaced by a threaded plug 310 mounted in a threaded hole 314 provided in the bottom of the housing means as seen in FIG. 9. This plug is provided with a flow rate control orifice 232A that serves the same function as flow rate control orifice 232 as seen in FIG. 3.

In operation of the embodiment of FIG. 9 the relatively hot control flow of oil is continuously circulated through modified control cylinder tl-A and outwardly through passage 312, flow rate control orifice 232A and hole 314 to an exterior reservoir, not illustrated, where the control flow is cooled prior to redelivery to the intake passage of the pump.

While the forms of embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

I claim:

1. In a hydraulic machine the combination of housing means including a housing inlet port and a housing outlet port; a cylinder barrel slideably disposed in said housing means and including a plurality of cylinders and an annular manifold, said cylinder barrel including an axially extending side wall provided with a barrel inlet port communicating with said cylinders and a barrel outlet port connecting saidrnanifold with said housing outlet port; a plurality of pistons disposed in said cylinders; a plurality of reaction plugs having inner ends slideably disposed in said cylinders and outer ends freely engaging said housing means; outlet valve means disposed in said barrel for conducting fluid from said cylinders to said manifold; cam means rotatably mounted in said housing means and in driving engagement with said pistons; piston return means engaging said pistons; and means for shifting said barrel in said housing means.

2. In a hydraulic machine the combination of housing means including a pressurized passage and inlet and outlet ports; a cylinder barrel disposed in said housing means and including a plurality of cylinders provided with intake and outlet ports and a' manifold, each of said outlet ports having an outlet at an axially extending outer surface of said cylinder barrel; a plurality of pistons disposed in said cylinders; a hollow outlet member radially shiftably mounted in said housing means and including an inner sur- [face slideably engaging said outer surface of said cylinder barrel and an outlet passage connecting said pressurized passage in said housing means with said manifold; cam means rotatably mounted in said housing means and in driving engagement with said pistons; piston return means engaging said pistons, and means for shifting said barrel in said housing means.

3. In a hydraulic machine the combination of housing means including an inlet port and an outlet port; a cylin der barrel slideably disposed in said housing means and including a plurality of cylinders provided with intake ports and a manifold; a plurality of pistons disposed in said cylinders; a control cylinder in said housing means; an annular piston disposed in said control cylinder and engaging said cylinder barrel for varying the location of said intake ports relative to said pistons; cam means rotatably mounted in said housing means and in driving engagement with said pistons; piston return means engaging said pistons; and means for conducting fluid from said manifold to said outlet port.

4. In a hydraulic machine the combination of housing means including an inlet port and an outlet port; a cylinder barrel slideably disposed in said housing means and including an annular manifold and a plurality of cylinders provided with intake ports; a plurality of pistons disposed in said cylinders; shaft means including a cam engaging said pistons; a piston return yoke connected to said pistons; means biasing said yoke against said pistons; means for conducting fluid from said manifold to said outlet port; and means for shifting said barrel in said housing means.

5. In a hydraulic machine the combination of housing means including an inlet port and an outlet port; a cylinder barrel slideably disposed in said housing means and including a plurality of cylinders provided 'with intake ports, a manifold, and an outer Wall provided with a plurality of axially extending guides; a plurality of bearing members disposed between said guides and said casing means; cam means rotatably mounted in said housing means and in driving engagement with said pistons; piston return means engaging said pistons; means for conducting fluid from said manifold to said outlet port; and means for shifting said barrel in said housing means.

6. A hydraulic machine comprising, in combination, housing means including a pressurized passage; a cylinder barrel slideably mounted in said housing means and including a plurality of cylinders, a central axially extending bore, a plurality of axially extending outer surfaces, and a plurality of intake and outlet ports each of which communicates with one of said cylinders and extends :to one said outer surfaces; a plurality of pistons disposed in said cylinders; shaft means including a cam engaging said pistons; a hollow member moveably mounted in said housing means and including an inner surface slideably engaging one of said surfaces on said cylinder barrel and a passage means connecting said pressurized passage in said housing means with one of said outlet ports; means for axially shifting said cylinder barrel in said housing means for varying the location of certain of said intake ports relative to said pistons; a piston return yoke engaging said pistons,

and yoke biasing means slideably disposed in said axially extending bore and in force transmitting relationship between said housing means and said yoke.

7. A hydraulic machine comprising, in combination, housing means including a control cylinder; a cylinder barrel slideably mounted in said housing means and including a plurality of cylinders, a central axially extending bore, a plurality of axially extending outer surfaces, and a plurality of outlet ports each of Which com municates with one of said cylinders and extends to one i of said outer surfaces; a plurality of pistons disposed in said cylinder; shaft means including acam engaging said pistons; a barrel driving piston in said control cylinder and engaging said cylinder barrel; a hollow member movably mounted in said housing means and including an inner surface slideably engaging one of said outer surfaces of said cylinder barrel and a passage means having an inner passage end communicating with one of said outer ports and an outer passage end communicating with said control cylinder; a piston return yoke engaging said pistons; and yoke biasing means slideably disposed in said axially extending bore and in force transmitting relationship between said housing means and said yoke.

8. A hydraulic machine comprising, in combination, housing means including a pressurized passage; a cylinder barrel slideably mounted in 'said housing means and including a plurality of cylinders, a central axially extending bore, a plurality of axially extending outer surfaces, and a plurality of intake and outlet ports each of which communicates with one of said cylinders and extends to one of said outer surfaces; a plurality of pistons disposed in said cylinder; a plurality of reaction plugs including inner ends disposed in said cylinders and outer ends engaging an end of said housing means; shaftmeans including a cam in driving engagement with said pistons; piston return means including a member slideably carried in said axially extending bore for biasing said pistons against saidcam; a hollow member moveably mounted in said housing means and including an inner surface slideably engaging one of said outer surfaces on said cylinder barrel and a passage means connecting said pressurized passage in said housing means with one of said outlet ports; and means for axially shifting said cylinder barrel in said housing means for varying the location of said intake ports relative to said pistons.

9. A hydraulic machine comprising, in combination, housing means; a cylinder barrel including a central axially extending bore, a plurality of axially extending cylinders, and a plurality of intake ports; 'a plurality of pistons disposed in said cylinders; shaft means including a cam engaging said pistons; a piston return yoke engaging said pistons, a piston return rod slideably disposed in said axially extending bore in said cylinder barrel and engaging said yoke; compression spring means operative between said casing means and said piston return yoke; and means for axially shifting said cylinder barrel in said housing means for varying the location of certain of saidintake ports relative to said pistons.

10. In a hydraulic machine'the combination of hous ing means; a'cylinder barrelslideably disposed insaid housing means and incluidng a cylinder provided with an intake port and an outlet port axially spaced from said intake port; a piston disposed in said cylinder and including a cavity, said piston controlling said intake port; a check valve in said cavity in communication with said intake port; means for axially shifting said cylinder barrel in said housing means for varying the location of said intake port relative to said piston. i

11. in a hydraulic machine the combination of housing means providing a source of fluid; a cylinder barrel slideably disposed in said housing means and including a cylinder provided with an intake port and an outlet port axially spaced from said intake port; a piston disposed in said cylinder controlling said intake port and including a cavity communicating with said source of fluid; a check valve in said cavity; means for'axia'lly shifting said cylinder barrel in said housing means for varying the location of said intake port relative to said piston.

12. In a hydraulic machine the combination of housing means; a cylinder barrel slideably disposed in said housing means and including a plurality of cylinders provided with ports, a discharge manifold communicating with certain of said ports, and an axially extending bore communicating with said manifold; a plurality of pistons disposed in said cylinders; a plurality of reaction plugs having inner ends slideably disposed in said cylinders and outer ends freely engaging said housing means; means for axially shifting said cylinder barrel in said housing means for varying the location of said ports relative to said pistons; and a reaction pin slideably disposed in said bore and in force transmitting relationship with said housing means.

13. In a hydraulic machine the combination of housing means; a cylinder barrel slideably disposed in said housing means and including a plurality of cylinders provided with ports, a discharge manifold communicating with certain of said ports, and an axially extending bore communicating with said manifold, each of said ports having an outlet at an axially extending outer surface of said cylinder barrel; a plurality of pistons disposed in said cylinders; a hollow outlet member mounted in said housing means and including an inner surface slideably engaging said outer surface of said cylinder barrel; means for axially shifting said cylinder barrel in said housing means for varying the location of said ports relatively to said pistons; and a reaction pin slideably disposed in said bore and in force transmitting relationship with said hous ing means.

14-. In a hydraulic machine the combination of housing means; a cylinder barrel slideably disposed in said housing means and including a plurality of cylinders provided with ports, a discharge manifold communicating with certain of said ports, and an axially extending bore communicating with said manifold; a plurality of pistons disposed in said cylinders; a control cylinder in said housing means; an annular piston disposed in said control cylinder and engaging said cylinder barrel for varying the location of said ports relative to said pistons; and a reaction pin slideably disposed in said bore and in force transmitting relationship with said housing means,

References Cited by the Examiner UNITED STATES PATENTS 1,252,875 1/18 Ashmusen 103-163 1,710,567 4/29 Carey 1 103-162 1,817,063 8/31 Carrie et a1. m 103-162 2,369,134 2/45 Cameron 103-173 2,444,550 7/48 Ashton a 103l73 2,502,546 4/50 Adams 103162 2,543,624 2/51 Gabriel 103162 2,619,041 11/52 Born 103-162 2,684,630 7/54 Widmer et al. 1O3-173 2,732,805 1/56 Lucien 103173 2,733,666 2/56 Poulos 103-162 2,945,444 7/60 Leissner 103-173 2,953,099 9/60 Budz-ich 103162 2,990,781 7/61 Tuck et a1. s 10 3-173 2,992,619 7/61 Nilges' 103162 3,002,528 10/61 Leissner 103-173 3,006,284 10/61 Pitt et al 103162 3,045,604 7/62 Hahn 103-473 FOREIGN PATENTS 1,202,109 7/59 France. 1,256,205 2/61 France.

(Corresponding US. 3,087,432). 433,571 4/23 Germany. 441,952 6/25 Germany. 556,384 7/29 Germany. 411,189 12/45 Italy.

LAURENCE V. EFNER, Primary Examiner.

JOSEPH H. BRANSON, 111., Examiner. 

1. IN A HYDRAULIC MACHINE THE COMBINATION OF HOUSING MEANS INCLUDING A HOUSING INLET PORT AND A HOUSING OUTLET PORT; A CYLINDER BARREL SLIDEABLY DISPOSED IN SAID HOUSING MEANS AND INCLUDING A PLURALITY OF CYLINDERS AND AN ANNULAR MANIFOLD, SAID CYLINDER BARREL INCLUDING AN AXIALLY EXTENDING SIDE WALL PROVIDED WITH A BARREL INLET PORT COMMUNICATING WITH SAID CYLINDERS AND A BARREL OUTLET PORT CONNECTING SAID MANIFOLD WITH SAID HOUSING OUTLET PORT; A PLURALITY OF PISTONS DISPOSED IN SAID CYLINDERS; A PLURALITY OF REACTION PLUGS HAVING INNER ENDS SLIDEABLY DISPOSED IN SAID CYLINDERS AND OUTER ENDS FREELY ENGAGING SAID HOUSING MEANS; OUTLET VALVE MEANS DISPOSED IN SAID BARREL FOR CONDUCTING FLUID FROM SAID CYLINDERS TO SAID MANIFOLD; CAM MEANS ROTATABLY MOUNTED IN SAID HOUSING MEANS AND IN DRIVING ENGAGEMENT WITH SAID PISTONS; RETURN MEANS ENGAGING SAID PISTONS; AND MEANS FOR SHIFTING SAID BARREL IN SAID HOUSING MEANS. 